Vehicles typically employ suspension systems that generally include a system of springs, dampers, also known as shock absorbers, and linkages that connect a vehicle body to the vehicle's wheels. The majority of forces acting on the vehicle body are transmitted through contact patches between the road and the tires. One of the main objectives of a vehicle suspension is to maintain the contact between the vehicle's road wheels and the road surface and dampen movement of a sprung mass of the vehicle which provides a smoother ride. Additionally, the design of the suspension also influences the height of the vehicle body relative to the road surface.
Vehicle suspension systems generally contribute to the vehicle's road-holding/handling and braking, as well as provide comfort and reasonable isolation from road noise, bumps, and vibrations to the vehicle occupants. Because these objectives are generally at odds, the tuning of suspensions involves finding a compromise that is appropriate to each vehicle's intended purpose. Some suspension systems are passive, so that preload, spring rate, and ride height of the vehicle are nonadjustable, single predetermined values determined by the design of the damper assembly. In some systems, preload, spring rate, and ride height are variable, but not all in a controlled manner. Other suspension systems are actively controlled, so that the spring rate or the preload of the vehicle can be varied.